A known apparatus is arranged to estimate viscosity of fuel and, based on the estimated value, control a discharge quantity of a fuel pump, as disclosed, for example, in Patent Document 1 (JP-A-9-287540). In the known art, the viscosity and concentration of the fuel is estimated according to, for example, temperature or properties of the fuel and the discharge quantity of the fuel pump is calculated from these estimated values.
Prior Art Documents
Patent Document
Patent Document 1: JP-A-9-287540